Document falsification and product counterfeiting are significant problems that have been addressed in a variety of ways. One of the more successful approaches has been the use of latent or hidden images applied to or printed on objects to be protected. These images are generally not viewable without the assistance of specialized devices that render them visible.
One approach to the formation of a latent image is to optically encode the image so that, when printed, the image can be viewed only through the use of a corresponding decoding device. Such images may be used on virtually any form of printed document including legal documents, identification cards and papers, labels currency, stamps, etc. They may also be applied to goods or packaging for goods subject to counterfeiting.
Objects to which an encoded image is applied may be authenticated by decoding the encoded image and comparing the decoded image to an expected authentication image. The authentication image may include information specific to the object being authenticated or information relating to a group of similar objects (e.g., products produced by a particular manufacturer or facility). Production and application of encoded images may be controlled so that they cannot easily be duplicated. Further, the encoded image may be configured so that tampering with the information on the document or label is readily apparent.
Authentication of documents and other objects “in the field” has typically required the use of hardware decoders such as lenticular or micro-array lenses that optically decode the encoded images. These lenses must have optical characteristics that correspond to the parameters used to encode and apply the authentication image and must be properly oriented in order for the user to decode and view the image. Lens-based decoders are typically separate from the objects being authenticated so that a single decoder can be used to authenticate many objects. For some objects, however, the decoder can be attached to or made an integral part of the object itself. Such self-authenticating objects are described in U.S. Pat. No. 7,114,750 and U.S. application Ser. No. 11/506,678, filed Aug. 18, 2006, both of which are incorporated by reference herein in their entirety.
Though hardware decoders have proven a valuable tool, they have inherent limitations. For example, because they can only be used for encoded images with corresponding characteristics, hardware decoders are relatively inflexible tools. Further, authentication using a hardware decoder generally requires on-site visual comparison of the decoded image to the authentication image by a human inspector. This raises accuracy and security concerns.
Accordingly, software-based decoders have been developed that can decode optically encoded images provided in digital form. These digital encoded images may be original digital images that have not been printed or they may be scanned-in digital images of encoded images that have been printed on an object. Software-based decoders are highly flexible in that they can be used to decode images having a variety of encoding characteristics. Also, they can be used to authenticate objects either by image comparison or by comparison of data extracted from a decoded image to object-related information.